Model analysis on thermal UV-cutoff effects on the critical boundary in hot QCD

TL;DR

This paper investigates how thermal UV-cutoff effects influence the critical boundary in hot QCD, comparing lattice simulations and chiral models, and demonstrates that UV-cutoff effects can explain discrepancies in critical mass predictions.

Contribution

It quantitatively analyzes the impact of temporal UV-cutoff effects on the critical boundary in hot QCD using a modified NJL model with finite Matsubara frequencies.

Findings

Critical mass decreases in lattice QCD as continuum limit is approached.

Finite N_tau in NJL model increases the critical mass, aligning with lattice results.

UV-cutoff effects are significant in understanding discrepancies between models and lattice simulations.

Abstract

We study the critical boundary on the quark-mass plane associated with the chiral phase transition in QCD at finite temperature. We point out that the critical boundaries obtained from the Lattice QCD simulation and the chiral effective model are significantly different; in the (Polyakov-loop coupled) Nambu--Jona-Lasinio (NJL) model we find that the critical mass is about one order of magnitude smaller than the value reported in the Lattice QCD case. It is known in the Lattice QCD study that the critical mass goes smaller in the continuum limit along the temporal direction. To investigate the temporal UV-cutoff effects quantitatively we consider the (P)NJL model with only finite $N_\tau$ Matsubara frequencies taken in the summation. We confirm that the critical mass in such a UV-tamed NJL model becomes larger with decreasing $N_\tau$, which demonstrates a correct tendency to explain the difference between the Lattice QCD and chiral model results.